Palladium is known as a useful catalyst since it induces various conversion reactions in organic synthesis. However, this metal has many problems in direct use as a catalyst because it is expensive and in addition, it loses partially its activity on contact with air and cannot be used repeatedly. Fixation of palladium on a polymer as a technology to solve these problems has been attempted and various reactions using palladium fixed on a polymer have been reported frequently so far. However, any of conventional palladium fixed on a polymer still has a common problem that catalyst recovery rate is low and activity decreases in repeated use, although stability of the catalyst itself is improved.
For example, the present inventors created a microcapsulated metal catalyst by fixing a palladium compound such as a palladium complex compound, an organic palladium compound, an inorganic salt and an organic salt, on a polystyrene-type compound, a polymer compound having an aromatic ring (for example, see the specification of Japanese application; JP-2001-59742). However, the above microcapsulated metal catalyst turned out to be difficult to use for a reaction employing a general organic solvent, because any of polymer compounds used as carriers is a non-crosslinked type and has defect of easily dissolving in an organic solvent to be used for a common organic reaction, such as methylene chloride, tetrahydrofuran, benzene and toluene. Because the polymer compound to be used as a carrier of the above microcapsulated metal catalyst was a non-crosslinked type, said metal-catalyst composition agglomerated easily, resulting in smaller surface area of said metal-catalyst composition, which caused a problem of very low catalyst efficiency due to smaller amount of actually functioning catalyst compared with an amount of the metal carried on a polymer carrier. Another problem was that raw materials or reaction products were caught into a carrier polymer constituting a catalyst composition in a reaction using these metal catalysts.
To solve these problems, the present inventors studied use of a crosslinked polymer carrier obtained by crosslinking with divinylbenzene or the like, as the above polystyrene-type polymer compound. However, it turned out to be impossible to fix a metal on polystyrene crosslinked by divinylbenzene, which is insoluble in a general organic solvent, because it was necessary to dissolve a polymer carrier in a solvent in order for the polymer to carry the metal physically.
On the other hand, a method for fixing a metal catalyst on a crosslinked polymer to which an ion-exchange group is introduced has been known as a method for fixing a metal catalyst on such a crosslinked polymer carrier (see Jp-A-59-27840, for example). However, a metal catalyst carried on a carrier obtained by such a method was sometimes difficult to use repeatedly due to leakage of the carried metal catalyst depending on properties of liquid to be used with.
In such situations, a more versatile new metal catalyst carried on a crosslinked polymer wherein the polymer carrier is insoluble in an organic solvent and the carried metal hardly leaks and can keep its activity in repeated use has been required.